Damage resistant plate type heat exchanger



Sept. 13, 1960 E. L. LADD 2,952,445

DAMAGE RESISTANT PLATE TYPE HEAT EXCHANGER Filed June 25, 1958 V o" I 1 f I H H m H do ATTORNE? United States Patent DAMAGE RESISTANT PLATE TYPE HEAT EXCHANGER Edward L. Ladd, Dayton, Ohio, assignor to United Aircraft Products, Inc., Dayton, Ohio, a corporation of Ohio Filed June 25, 1958, Ser. No. 744,607

2 Claims. (Cl. 257-245) This invention relates to heat transfer equipment and particularly to plate type exchangers constructed with a view to maximum weight conservation.

Plate type exchangers commonly are comprised of a plurality of superposed spaced apart plates closed at selected marginal edges to define alternate fluid flowing ducts for different fluids to be brought into heat transfer relation, the exchange of heat taking place between adjacent ducts through a separating plate. Frequently corrugated fin material is placed within the ducts to aid in the absorption and transfer of heat. For aircraft use, where weight conservation is necessarily a prime objective, it is customary to construct the exchanger of light weight metals such as a aluminum alloys. Also, the plates are made thin and the fin material is formed of still thinner, ductile sheet metal. So fabricated, an exchanger is effectively reduced in weight but other problems are introduced such as the obtaining of an inexpensive, secure means of uniting the component parts of the exchanger. Also, in some uses of the exchanger high fluid pressures are encountered which may destroy too lightly a constructed device, and further, if the exchanger is in use disposed in an ambient air stream damage may result to the foil-like fins from particles entrained in the air. Extensive damage to the exchanger or at least the closing off of portions of the fluid flowing duct may result therefrom.

The instant invention has in view a concept of a light weight heat exchanger specially constructed for operation under high pressures and for resistance to air flow damage as described. Features of such concept lie in a new means of fabrication wherein the fin material serves the dual purpose of more effectively transferring heat and of acting as tie strips positively to connect adjacent plates to one another. Also, an all brazed construction is contemplated obviating the need for separable connecting devices, and, still further, a generally new fin structure is proposed characterized by the use of a relatively short length fin at the entrance end of the duct made of a heat treatable, damage resistant material and spaced from following fin material in a manner to define therewith a plenum chamber for lateral distribution of the flowing fluid.

Other objects and structural details of the invention will appear from the following description when read in connection with the accompanying drawing, wherein:

Fig. 1 is a fragmentary view of a plate type heat exchanger in accordance with the illustrated embodiment of the invention, shown in a longitudinal section taken substantially along the line 11 of Fig. 2;

Fig. 2 is a view in cross section taken substantially along the line 2-2 of Fig. 1;

Fig. 3 is a view in top longitudinal section, taken substantially along the line 33 of Fig. l; and

Fig. 4 is a view in perspective of the portion of the illustrative heat exchanger shown in Figs. 1 to 3.

Referring to the drawing, a heat exchanger in accordice ance with the illustrated embodiment of the invention comprises a series of stacked plates of a number selected in accordance with the number of fluid passes or fluid flowing ducts to be provided by the exchanger. In the example shown, four plates, 1, 2, 3 and 4 are shown. These plates have substantially the same configuration and are made of a thin light weight metal. The plates 1 and 2 are held spaced apart by marginal strips 5. Similar strips 6 hold the plates 3 and 4 in spaced relation and there is interposed between the plates 2 and 3 strip fins 7 and 8, there being further disposed between the plates 2 and 3 marginal strips 9 (one shown) as seen in Fig. 4. The fins 7 and 8 are spaced apart and define between them a plenum chamber 10.

The arrangement is one devised to bring two fluids into heat transfer relation through separating plates. To this end the marginal pieces 9 close opposite side edges of adjacent plates 2 and 3 and define therewith a fluid flowing duct open at its opposite ends for flow therethrough as indicated by the arrows in Fig. 1. The marginal pieces 5 are disposed at right angles to the pieces 9 and define with the plates 1 and 2 a duct for flow at right angles to the direction of flow in the space between plates 2 and 3. The marginal pieces 6 are arranged like the pieces 5. Thus, above and below the duct defined by plates 2 and 3, through which a first fluid flows as indicated by the arrows in Fig. l, are arranged other ducts for flow of another or other fluids in heat transfer relation tothe first fluid through respective plates 2 and 3. As indicated in Fig. 2, the upper and lower ducts as described may communicate with a common header 11 to receive a fluid flow. In the illustrated instance the header 11 and its communicating ducts constitute a part of a closed fluid flowing system, for example a lubricant circulating system. The duct for flow of the first fluid, on the other hand, is open to ambient air flow.

In the installation of the exchanger it is placed in an air duct or the like with the ram force of the moving air applied to that face of the exchanger offering open passes through the plates 2 and 3. The arrangement of the fins 7 and 8- is such as to present the longitudinal edges thereof to such air flow, the air flowing lengthwise along the fins which are corrugated to define in effect a plurality of separated longitudinal passes through the duct of the exchanger. The alternate hills and valleys of the fin are respectively in contact With the plates 2 and 3 to close off such individual passes and with the further eflect aiding in a more thorough absorption of heat from or into the flowing fluid. According to a feature of the invention the fin 7 is short in length relatively to the fin 8 and is made of a heat treatable material in order that it can be hardened and made resistant to abrasion and impact damage from particles in the flowing air stream. According to this. concept, therefore, the heat exchanger presents a hard, relatively unyielding face to the ram air there being presented only the edges of plates 1, 2, 3 and 4, the marginal pieces 5 and 6 and the edges of the fin 7. The marginal pieces 5 and 6 may also be hardened as the fin 7 so that the entire face of the exchanger is made damage resistant. The separation of the fin means 78 into two parts reduces the cost of the assembly inasmuch as the major portion of the fin means is represented by the fin 8 which may be made of the conventional untreated aluminum alloy. Also, however, such separation makes possible the plenum chamber 10 wherein a free lateral distribution of the flowing air is possible. In the presence of this chamber, therefore, a stoppage in one of the passes through the fin 7 may occur without complete loss of heat transfer ability in the longitudinal area of the exchanger in which the blocked pass lies. Should a pebble or a deformed fin portion or the like block one of the longitudinal passes through the fin 7 the air moving through the other parallel passes is free to redistribute itself in a lateral sense within the plenum chamber and to. flow through all of the passes as defined bythe fin gtincluding the one aligned with the blockedpass in The construction is one lending itself to effective fabrication. by a brazing or like process uniting the component parts securely and without likelihood of damage due to internal pressure. In the assembly of the exchanger the several parts are brought together in the manner illustrated and held in, a suitable fixture while dipped in a brazing process or otherwise unitarily connected in'a similar metal working process. Since the hills and valleys of the fin material 7 and 8 are in contact with adjacent plates these portions are united with the plate. Anueflective heat transfer connection so is made, and, in addition, a plurality of positive ties is formed between adjacent plates in a manner to resist bulging or speration of such-plates by the contained pressure of the fluids in the heat exchanger. While fin structure has been shown. only in the airflow passes it will be understood that fins may also be interposed in the closed flowing system represented by the ducts between plates 1 and 2 and between plates 3 and 4. These plates also will thus be securely tied together through the fin means. The fins are made of a thin and ductile material corrugated or crimped to the configuration shown and placed between adjacent plates of the heat exchanger with side edges of the fin strip in contact with the marginal closure pieces, the strip being in effect confined along its side edges by such marginal pieces,

What is claimed is:

1. A plate type heat exchanger constructed for weight conservation and damage resistance, including a pair of spaced apart thin metal plates of four side configuration and aligned in superposed relation to one another, closure means received between opposing side edges of said plates and defining with said platesa fluid flowing duct having opposed open entrance and exit ends, strip fin means installed in said duct including first and second strip fins made of foil-like sheet metal material of the same gauge and heat transfer capabilities and crirnped to present alternate hills and valleys in contact respectively with the opposing surfaces of said plates, one of said strip fins being relatively shorter in length than the other and made of heat treatable material and further being stationed at the entrance end of the duct ahead of the other fin, said other fin being, spaced from said one fin a distance corresponding to a substantial part of the length of said one fin to define intermediate the fins a plenum chamber for lateral distribution of fluid and said other fin extending uninterruptedly throughout the remaining length of said duct to said exit end thereof, and means uniting the assembly comprising said plates, said closures and said fins into an integrated structure.

2. A plate type heat exchanger according to claim 1, characterized by additional thin metal plates above and below said pair of plates, and closures installed in opposing side edges of adjacent plates above and below said pair of plates to. define other fluid flowing ducts in transverse relation to the first said fluid flowing duct, the last said closures being made of heat treatable material to present in conjunction with said one strip fin a damage resistant face on one side of the heat exchanger.

References Cited in the file of this patent UNITED STATES PATENTS 1,899,080 Dalgliesh Feb. 28, 1933 2,376,749 Belaieff May 22, 1945 2,566,310 Burns et al. Sept. 4, 1951 2,606,007 Simpelaar Aug. 5, 1952 2,869,835 Butt Jan. 20, 1959 enema. 

